When a person uses hair products on their hair, those same hair products can migrate to the skin through various mechanisms. For example, when shampooing and/or conditioning hair, the shampoo and conditioner unavoidably come into contact with the scalp, face, neck, chest, shoulders, and back, either through direct contact or as they are rinsed off and run down the skin in the shower.
Many hair care products, including rinse off products, such as shampoos and conditioners, are also designed to leave a residue even after the product is subsequently rinsed out of the hair. Leave in hair care products by design are not rinsed out and always leave a residue. This residue may be good for the hair, but can often cause problems for the skin. This residue can be deposited on the skin directly by direct contact with the skin on the scalp, and, for example, by dripping down from the hair to the face after application as well as when it runs down the person's face, neck, chest, shoulders, and/or back in the shower. This residue can also be deposited on a person's skin indirectly, when an object successively comes into contact with the person's hair, and then their skin. For example, if the person dries their hair with a towel, the residue can be transferred to other parts of their body via the towel; residue may also be transferred from a person's hair to their face from a pillowcase.
Most hair care products are developed without consideration of the impact that the product will have on the user's skin, despite the fact that contact with the skin with each use is unavoidable. Many hair care products can also build up on the skin or scalp over time, particularly if the hair care product is intended to be left in for days at a time; as a result, the hair care products may have a dramatically detrimental effect on the skin of a user. Many hair care products also contain ingredients that can trigger irritation of the skin in some users. In some cases, hair and skin treatments may also have incompatible regimens; for example, a person with parched hair strands resulting from coloration of their hair, may require hair products with significant amounts of oils and conditioning agents, some of which can be comedogenic to the skin.
According to the American Academy of Dermatology [AAD], a “comedo” is an “acne lesion”, a hard blockage created from an excess of sebum combined with keratin (skin debris) in a pore which can lead to whiteheads, blackheads and pimples. Accordingly, the term, “comedogenic”, refers to ingredients or products that have a tendency to block pores and promote comedones or acne.
Those with curly and/or frizzy hair may use smoothing products that traditionally contain ingredients such as oils and conditioning agents that can be comedogenic, or can become comedogenic in combination with other ingredients. For example, some common hair smoothing products, such as some silicone hair smoothing products, have not been found to be significantly comedogenic on their own, but have been found to increase the penetration of other ingredients in a formulation, which may result in a more comedogenic product. This means that hair care products can, in many cases, contribute to and exacerbate skin conditions such as acne (or “acne vulgaris”), the most common skin disease in the United States.
Acne vulgaris affects up to 50 million people in the United States alone. Acne is not just a condition that affects teenagers. Acne is highly prevalent in adult women, with one study showing that 45% of women aged 21-30, 26% aged 31-40, and 12% aged 41-50 had clinical acne. Adult acne in women is also on the rise. According to the American Academy of Dermatology (AAD), acne can contribute to depression, anxiety, and poor self-image. It can also leave permanent scars.
Acne may arise when hair follicles (pilosebaceous units) become clogged. Acne is characterized by comedones, clogged pores in the skin, which can either be open comedones (“blackheads”) or closed comedones (“whiteheads”). Acne is also characterized by pimples, which can appear as inflammatory papules or pustules, cysts, or nodules.
Acne is caused by several major mechanisms: inflammation, oil/sebum, follicular hyperkeratinization, propionibacterum acnes (p. acnes), a bacteria, and hormones. Sebum, an oily substance secreted by the sebaceous glands of the skin, can cause dead skin cells to stick together, which can clog pores and plug hair follicles, causing acne. Sebum secretion has been correlated with acne severity, with high sebum secretion levels tended to be correlated with more severe acne; in some cases, a high sebum secretion rate may even be the decisive factor in inflammatory acne.
P. acnes is a bacteria that lives on the skin and can also get inside the follicle and contribute to inflammation, causing inflammatory acne lesions, including papules, cysts, and nodules. Conventional belief was that all inflammatory acne lesions arose from comedones. Recently, acne has been identified to be a primary inflammatory condition. There is evidence that inflammation plays a role at all stages of acne development, and can even be observed subclincally before the formation of comedones.
Acne can also be caused or exacerbated by certain cosmetics or styling products. “Acne cosmetica” is a form of acne that is caused by or exacerbated by the use of certain cosmetic products, including, though not limited to, makeup and sunscreen. “Acne cosmetica” typically results from a chemically-induced plugging of the hair follicles by these products. Certain cosmetic products can also produce folliculitis, or inflammation of the hair follicle, which appears as small bumps on the skin that can be skin-colored, pink, or red, having an appearance similar to acne.
For example, “pomade acne” is a similar condition to “acne cosmetica,” also resulting from chemically-induced plugging of the hair follicles, and characterized by bumps on the forehead caused by oily hair care styling products. This condition was originally described primarily in African American men. Both “acne cosmetica” and “pomade acne” may also be referred to generally as “acneiform eruptions.” Pomade acne has more recently been described as being an issue in all skin types, in both men and women due to hair products that smooth the hair, add shine, and reduce frizz. These products can contain oils, and waxes that clog pores, trap bacteria, and cause inflammation. Users of these products may find that these products are transferred to their pillow at night if left in their hair; as a result, users of these products may find that their faces are rolling around in oily, waxy, hair products all night. (Other hair products, particularly products not designed to be washed out within a day or so, may also cause similar problems.)
The ingredients in these hair products that clog pores and cause acne are not limited to oils and waxes used for styling and conditioning, as other ingredients can be problematic. Comedogenic or potentially comedogenic components include PVP/DMAPA acrylates, cyclopentasiloxane, panthenol, dimethicone, some silicones (typically to a mild degree), Quaternium-70, oils, and petrolatum. These ingredients may be comedogenic themselves, or, as mentioned previously, may enhance the comedogenicity, irritation, and/or allergic potential of other ingredients. For example, petrolatum itself is non-comedogenic, but is occlusive and can trap moisture and other ingredients in the hair follicles, causing stronger reactions to these ingredients.
For patients with adult acne, the AAD recommends using personal care products, including hair care products, which have one of the following labels: “non-comedogenic,” “non-acnegenic,” “oil-free,” or “won't clog pores.” However, these labels are not typically found on hair care products because hair care products are not typically formulated to be “non-comedogenic,” “non-acnegenic,” or “oil-free.” Currently, it is not standard to test hair care products for comedogenicity or acnegenicity, or to have oil-free hair care products for acne-prone skin. In fact, there is a trend in the beauty industry to add oils to hair care products.
Many common hair care products, such as shampoos, conditioners, and other hair care products, contain oils that are or have the potential to be comedogenic. As mentioned, other products, such as silicones, can also be comedogenic in combination with other products in a formulation. Many leave-in products also contain significant quantities of these oils and silicones that can be comedogenic, including, though not limited to, styling creams, gels, pomades, hairsprays, smoothing serums, heat styling sprays, anti-frizz serums, heat-protectants, and shine sprays. Other materials in hair care products are also potentially comedogenic.
A list of comedogenic or potentially comedogenic materials includes, but is not limited to, acetylated lanolin, acetylated lanolin alcohol, algin, almond oil, apricot kernel oil, avocado oil, grapeseed oil, bismuth oxychloride, butyl stearate, carrageenan, ceteareth 20, cetyl acetate, cocoa butter, coconut oil, coal tar, hydrogenated oils, D & C Red #17, D & C Red #21, D & C Red #3, D & C Red #30, D & C Red #36, decyl oleate, disodium oleamido peg-2 sulfosuccinate, lanolin, lanolin derivatives, ethylhexyl palmitate, glyceryl stearate SE, glyceryl-3-diisostearate, hexadecyl alcohol, hydrogenated vegetable oil, isocetyl alcohol, isocetyl stearate, isodecyl oleate, isopropyl isostearate, isopropyl myristate, isopropyl palmitate, isostearyl isostearate, isostearyl neopentanoate, laureth-23, laureth-4, lauric acid, mink oil, myristic acid, myristyl lactate, myristyl myristate, octyl palmitate, octyl stearate, oleic acid, oleates, oleth-3, oleyl alcohol, olive oil, peg 200 dilaurate, PEG 8 stearate, PG monostearate, PPG 2 myristyl propionate, polyglyceryl-3-diisostearate, propylene glycol monostearate, sesame oil, sodium laureth sulfate, sodium lauryl sulfate, sorbitan oleate, soybean oil, steareth 10, stearyl heptanoate, sulfated oils, triethanolamine, wheat germ glyceride, wheat germ oil, and certain conditioning agents. Occlusive agents, including some of the above materials, can often contribute to comedogenicity and acne. See Fulton, J. Soc. Cosmet. Chem., 40, 321-333 (November/December 1989) “Comedogenicity and irritancy of commonly used ingredients in skin care products” for a discussion of comedogenic materials.
In addition, most shampoos contain potentially irritating surfactants, such as sulfate-based surfactants; for example, sodium lauryl sulfate and ammonium lauryl sulfate are common surfactants that can cause irritation. Irritation to the skin can produce folliculitis and small papules on the skin, which may appear similar to acne. The folliculitis that occurs is indistinguishable from acne to the majority of hair care product users. Irritation of the follicle can also increase penetration of other materials in the hair care product into the skin follicles, increasing the potential comedogenicity and acnegenicity of many materials that could come into contact with the skin, including other materials in the hair care product formulation.